Generally, in a technology of detecting an obstacle of a vehicle, an ultrasonic sensor provided in the vehicle is used. However, the ultrasonic sensor may erroneously sense the obstacle depending on a position at which it is mounted and the surrounding environment. In addition, in the case of detecting the obstacle using the ultrasonic sensor, a place at which the obstacle is not present is sensed by error due to a prominence or depression of the ground or disturbance of a sound source, such that an erroneous alarm may be issued. Therefore, reliability for detecting the obstacle is decreased.
Further, in the case of detecting the obstacle using the ultrasonic sensor, the obstacle may be detected only in a direction in which the ultrasonic sensor is mounted. That is, in order to detect the obstacle in all directions of the vehicle, ultrasonic sensors need to be mounted in all directions of the vehicle.